Organic and inorganic precipitates are both characteristic in the active hypogenic karst area of Buda Thermal Karst in Hungary. As an active system, it is a good natural laboratory to study ongoing precipitation processes. Because of anthropogenic influence and the complexity of spring environments, it is challenging to reveal all the governing factors in the process of precipitation. In situ experiments, i.e. artificially controlled natural systems simplify the complexity by adding, excluding or stabilizing influencing parameters during the experiment. CO₂ degassing drives changes in the physicochemical parameters of spring waters from the discharge along their flow path. The rate and spatial extension of these changes depend on local hydrogeological, geological, climatic, topographical etc. factors, affecting precipitation processes. In this study, two one-day-long in situ experiments were executed to examine the physicochemical parameter changes of thermal water in a tunnel. The integration of the results with reactive transport models revealed the physicochemical processes of ingassing and degassing and predicted CaCO₃ precipitation along the flow path. Small-scale roughness of the channel surface seemed to further influence pH and concentration of HCO₃⁻. After 6 weeks of thermal water flowing, organic precipitate (biofilm) formed close to the discharge and then, with a sharp change, inorganic precipitate (calcite) dominates a bit further from the discharge. In situ experiments and connected numerical simulations revealed the role of CO₂ degassing and calcite precipitation in the changes of physicochemical parameters, but organic precipitates also have to be considered near the discharge.

中文翻译：

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整合原位实验和数值模拟来揭示温泉中有机和无机沉淀的理化情况

有机和无机沉淀物都是匈牙利布达热岩溶的活跃的假性岩溶区的特征。作为一个活跃的系统，它是研究正在进行的降水过程的良好天然实验室。由于人为因素的影响和春季环境的复杂性，要​​揭示降水过程中的所有控制因素都具有挑战性。原位实验（即人工控制的自然系统）通过在实验过程中添加，排除或稳定影响参数来简化复杂性。一氧化碳₂脱气驱动泉水沿其流路从排出物中改变理化参数。这些变化的速度和空间扩展取决于当地的水文地质，地质，气候，地形等因素，从而影响降水过程。在这项研究中，进行了两个为期一天的原位实验，以检验隧道中热水的理化参数变化。结果与反应性运输模型的集成揭示了渗入和脱气的物理化学过程，并预测了沿流动路径的CaCO ₃沉淀。沟道表面的小规模的粗糙度似乎进一步影响pH和HCO的浓度₃ ^-。在热水流过6周后，靠近排放口形成了有机沉淀物（生物膜），然后急剧变化，无机沉淀物（方解石）在排放口附近占主导地位。原位实验和相关的数值模拟揭示了CO ₂脱气和方解石沉淀在理化参数变化中的作用，但在排放附近也必须考虑有机沉淀。